Requirements to video parameters while using face detection tool

When a face detection tool is in use, the following requirements must be met:

1. Minimum linear dimensions of a face to be detected are 24 pixels.
2. Maximum speed of a face to be detected is not to be more than a half of linear dimensions in pixels per frame (i.e. face overlapping between two adjacent frames must be not less than half-width and half-height of face).
3. A detection tool needs 8 frames to confirm face detection – otherwise, a face detection message won’t be sent.